Patent application title: PROJECTOR

Abstract:

A projector includes: a first solid-state light source device which
includes a first solid-state light source emitting main excitation light,
and a fluorescent layer converting main excitation light emitted from the
first solid-state light source to light including a first color light
component and a second color light component different from the first
color light component, and emitting converted light; a second solid-state
light source device which includes a second solid-state light source
emitting a third color light component different from the first color
light component and the second color light component; a light modulation
device modulating the first color light component, the second color light
component, and the third color light component in accordance with image
information; a projection optical system projecting the modulated light
components from the light modulation device as a projection image; and a
color light combining optical system combining light emitted from the
first solid-state light source device and the third color light component
emitted from the second solid-state light source device.

Claims:

1. A projector comprising:a first solid-state light source device which
includes a first solid-state light source emitting main excitation light,
and a fluorescent layer converting main excitation light emitted from the
first solid-state light source to light including a first color light
component and a second color light component different from the first
color light component, and emitting converted light;a second solid-state
light source device which includes a second solid-state light source
emitting a third color light component different from the first color
light component and the second color light component;a light modulation
device modulating the first color light component, the second color light
component, and the third color light component in accordance with image
information;a projection optical system projecting the modulated light
components from the light modulation device as a projection image; anda
color light combining optical system combining light emitted from the
first solid-state light source device and the third color light component
emitted from the second solid-state light source device.

2. The projector according to claim 1, further comprising:a first
collimation optical system parallelizing light emitted from the first
solid-state light source device; anda second collimation optical system
parallelizing the third color light component emitted from the second
solid-state light source device,wherein the color light combining optical
system is disposed in a region including an intersection between an
optical axis of the first collimation optical system and an optical axis
of the second collimation optical system to directly transmit light which
is converted by the fluorescent layer and emitted from the fluorescent
layer, to reflect the third color light component from the second
solid-state light source device, and to combine light emitted from the
first solid-state light source device and the third color light component
with each other.

3. The projector according to claim 2, further comprising:an excitation
light reflecting mirror located at the back of the first collimation
optical system to directly transmit light, which is converted by the
fluorescent layer and emitted from the fluorescent layer, and to reflect
main excitation light, which is emitted while not being converted by the
fluorescent layer, toward the fluorescent layer.

4. The projector according to claim 1,wherein main excitation light is a
blue light component,the first color light component is a red light
component,the second color light component is a green light component,
andthe third color light component is a blue light component.

5. The projector according to claim 4,wherein the first solid-state light
source and the second solid-state light source have the same temperature
characteristic.

6. The projector according to claim 1,wherein main excitation light is
ultraviolet light,the first color light component is a red light
component,the second color light component is a green light component,
andthe third color light component is a blue light component.

7. The projector according to claim 1, further comprising:a third
solid-state light source device which includes a third solid-state light
source emitting auxiliary excitation light,wherein the fluorescent layer
is configured such that auxiliary excitation light is input thereto in a
direction different from a direction in which main excitation light is
input, andthe fluorescent layer is configured to convert auxiliary
excitation light with main excitation light to light including the first
color light component and the second color light component and to emit
converted light.

8. The projector according to claim 7, further comprising:a first
collimation optical system parallelizing light emitted from the first
solid-state light source device;a second collimation optical system
parallelizing the third color light component emitted from the second
solid-state light source device; anda third collimation optical system
parallelizing auxiliary excitation light emitted from the third
solid-state light source device,wherein the color light combining optical
system is disposed in a region including an intersection between an
optical axis of the first collimation optical system, an optical axis of
the second collimation optical system, and an optical axis of the third
collimation optical system to directly transmit light, which is converted
by the fluorescent layer and emitted from the fluorescent layer, to
reflect the third color light component from the second solid-state light
source device, thereby combining light emitted from the first solid-state
light source and the third color light component with each other, and to
reflect auxiliary excitation light from the third solid-state light
source device such that auxiliary excitation light is input to the
fluorescent layer in an opposite direction to a direction in which main
excitation light is input from the first solid-state light source.

9. The projector according to claim 7,wherein main excitation light is a
blue light component,the first color light component is a red light
component,the second color light component is a green light component,the
third color light component is a blue light component, andauxiliary
excitation light is a blue light component.

10. The projector according to claim 9,wherein the first solid-state light
source, the second solid-state light source, and the third solid-state
light source have the same temperature characteristic.

11. The projector according to claim 7,wherein main excitation light is a
blue light component,the first color light component is a red light
component,the second color light component is a green light component,the
third color light component is a blue light component, andauxiliary
excitation light is ultraviolet light.

12. The projector according to claim 11, further comprising:an excitation
light reflecting mirror disposed in front of the color light combining
optical system to directly transmit light, which is converted by the
fluorescent layer and emitted from the fluorescent layer, and to reflect
main excitation light, which is emitted while being not converted by the
fluorescent layer, toward the fluorescent layer.

13. The projector according to claim 7,wherein main excitation light is
ultraviolet light,the first color light component is a red light
component,the second color light component is a green light component,the
third color light component is a blue light component, andauxiliary
excitation light is a blue light component.

14. The projector according to claim 13, further comprising:an excitation
light reflecting mirror disposed in front of the color light combining
optical system to directly transmit light, which is converted by the
fluorescent layer and emitted from the fluorescent layer, and to reflect
main excitation light, which is emitted while being not converted by the
fluorescent layer, toward the fluorescent layer.

15. The projector according to claim 7,wherein main excitation light is
ultraviolet light,the first color light component is a red light
component,the second color light component is a green light component,the
third color light component is a blue light component, andauxiliary
excitation light is ultraviolet light.

16. The projector according to claim 1,wherein the fluorescent layer is
formed of a layer containing a YAG-based fluorescent material, a
silicate-based fluorescent material, or a TAG-based fluorescent material.

17. The projector according to claim 1,wherein a function is provided to
remove a yellow light component from light from the first solid-state
light source device.

18. The projector according to claim 17, further comprising:a color
separating and guiding optical system separating the first color light
component, the second color light component and the third color light
component from light from the first solid-state light source device and
the second solid-state light source device, guiding the separated first,
second and third color light components to the light modulation device
respectively, and removing a yellow color light component from light from
the first solid-state light source device.

Description:

BACKGROUND

[0001]1. Technical Field

[0002]The present invention relates to a projector, and in particular, to
a projector using a solid-state light source.

[0003]2. Related Art

[0004]A projector is known which includes a single solid-state light
source device emitting white light, a color separating and guiding
optical system separating light from the single solid-state light source
device into a red light component, a green light component, and a blue
light component, a light modulation device modulating the respective
color light components from the color separating and guiding optical
system in accordance with image information, and a projection optical
system projecting the modulated light components from the light
modulation device as a projection image (for example, see
JP-A-2005-274957). According to the projector described in
JP-A-2005-274957, the three color light components which are obtained by
separating white light emitted from the single solid-state light source
device are used as the three color light components (red light component,
green light component, and blue light component) which are modulated by
the light modulation device. Unlike a projector which includes three
solid-state light source devices, the light-emission efficiency
(brightness per unit power) or the temperature characteristic (the change
of light amount with change in temperature) does not differ between the
solid-state light source devices. As a result, the color balance of the
projection image can be stabilized.

[0005]A projector is also known which includes a solid-state light source
device emitting a red light component, a solid-state light source device
emitting a green light component, a solid-state light source device
emitting a blue light component, a light modulation device modulating the
color light components from the respective solid-state light source
devices in accordance with image information, and a projection optical
system projecting the modulated light components from the light
modulation device as a projection image (for example, see
JP-A-2002-268140). According to the projector described in
JP-A-2002-268140, separate solid-state light source devices (a
solid-state light source device emitting a red light component, a
solid-state light source device emitting a green light component, and a
solid-state light source device emitting a blue light component) are
provided for the respective color light components (red light component,
green light component, and blue light component), and the three color
light components which are respectively emitted from the three
solid-state light source devices are used as the three color light
components (red light component, green light component, and blue light
component) which are modulated by the light modulation device. Thus, the
projection image can be brightened compared to a projector which includes
a single solid-state light source device.

[0006]However, according to the projector described in JP-A-2005-274957,
since white light including a red light component, a green light
component, and a blue light component is generated from the single
solid-state light source device, unlike a projector which includes three
solid-state light source devices, a significant thermal load is
concentrated on the single solid-state light source device. As a result,
it is difficult to further brighten the projection image.

[0007]According to the projector described in JP-A-2002-268140, it is
difficult to make the three solid-state light source devices respectively
emitting the red light component, the green light component, and the blue
light component (the solid-state light source device emitting the red
light component, the solid-state light source device emitting the green
light component, and the solid-state light source device emitting the
blue light component) the same light-emission efficiency or temperature
characteristic. For this reason, it is difficult to stabilize the color
balance of the projection image.

SUMMARY

[0008]An advantage of some aspects of the invention is that it provides a
projector capable of brightening a projection image compared to a
projector including a single solid-state light source device, and
stabilizing the color balance of the projection image compared to a
projector including separate solid-state light source devices for
respective color light components.

[0009]A projector according to an aspect of the invention includes a first
solid-state light source device which includes a first solid-state light
source emitting main excitation light, and a fluorescent layer converting
main excitation light emitted from the first solid-state light source to
light including a first color light component and a second color light
component different from the first color light component, and emitting
converted light, a second solid-state light source device which includes
a second solid-state light source emitting a third color light component
different from the first color light component and the second color light
component, a light modulation device modulating the first color light
component, the second color light component, and the third color light
component in accordance with image information, a projection optical
system projecting the modulated light components from the light
modulation device as a projection image, and a color light combining
optical system combining light emitted from the first solid-state light
source device and the third color light component emitted from the second
solid-state light source device.

[0010]According to this projector, the two color light components (first
color light component and second color light component) emitted from the
first solid-state light source device and the one color light component
(third color light component) emitted from the second solid-state light
source device are used as the three color light components (red light
component, green light component, and blue light component) which are
modulated by the light modulation device. Therefore, the thermal load
imposed on the respective solid-state light source devices can be reduced
compared to a projector which includes a single solid-state light source
device. As a result, the projection image can be brightened compared to a
projector which includes a single solid-state light source device.

[0011]According to this projector, two color light components (first color
light component and second color light component) from among the three
color light components (red light component, green light component, and
blue light component) which are modulated by the light modulation device
are generated by using a common solid-state light source (first
solid-state light source). Therefore, the color balance of the projection
image can be stabilized compared to a projector which includes separate
three solid-state light source devices for respective color light
components.

[0012]As a result, the projector according to the aspect of the invention
can brighten the projection image compared to a projector which includes
a single solid-state light source device, and can stabilize the color
balance of the projection image compared to a projector which includes
separate three solid-state light source devices for respective color
light components.

[0013]This projector includes the color light combining optical system
combining light emitted from the first solid-state light source device
and the third color light component emitted from the second solid-state
light source device. Therefore, it is not necessary to provide
exclusive-use optical systems for light emitted from the first
solid-state light source device and the third color light component
emitted from the second solid-state light source device, such that the
number of components can be reduced.

[0014]In the projector according to the aspect of the invention, when a
three-plate light modulation device is used as the light modulation
device, with the above-described configuration, a full color projector
can be constituted by using a color separating and guiding optical system
which is widely used at present.

[0015]In the projector according to the aspect of the invention, when a
single-plate light modulation device is used as the light modulation
device, with the above-described configuration, a full color projector
can be constituted by using a color wheel which is widely used at
present.

[0016]The projector according to the aspect of the invention may further
include a first collimation optical system parallelizing light emitted
from the first solid-state light source device, and a second collimation
optical system parallelizing the third color light component emitted from
the second solid-state light source device. The color light combining
optical system may be disposed in a region including at an intersection
between an optical axis of the first collimation optical system and an
optical axis of the second collimation optical system to directly
transmit light which is converted by the fluorescent layer and emitted
from the fluorescent layer, to reflect the third color light component
from the second solid-state light source device, and to combine light
emitted from the first solid-state light source device and the third
color light component with each other.

[0017]With this configuration, light (including the first color light
component and the second color light component) emitted from the first
solid-state light source device and the third color light component
emitted from the second solid-state light source device can be combined
together as parallel light.

[0018]The projector according to the aspect of the invention may further
include an excitation light reflecting mirror located at the back of the
first collimation optical system to directly transmit light, which is
emitted from the fluorescent layer, and to reflect main excitation light,
which is emitted while not being converted by the fluorescent layer,
toward the fluorescent layer.

[0019]Meanwhile, in the projector according to the aspect of the
invention, part of main excitation light emitted from the first
solid-state light source device may directly transmit the fluorescent
layer, which may cause degradation in light use efficiency, or
deterioration in color reproducibility or deterioration of the light
modulation device.

[0020]However, with the above-described configuration, main excitation
light having directly transmitted the fluorescent layer is input again to
the fluorescent layer and reused, such that light use efficiency can be
improved, and consequently the projection image can be further
brightened. Further, with the above-described configuration, main
excitation light can be removed from light from the first solid-state
light source device. As a result, color reproducibility or the light
modulation device can be prevented from being deteriorated due to main
excitation light.

[0021]In the projector according to the aspect of the invention, main
excitation light directly transmits the fluorescent layer and is
converted to parallel light by the first collimation optical system.
Then, parallel light is reflected by the excitation light reflecting
mirror, is focused by the first collimation optical system, and is
efficiently input to the light-emission region of the fluorescent layer.
Therefore, it is possible to suppress the spread of the light-emission
region due to the excitation light reflecting mirror being further
provided.

[0022]In the projector according to the aspect of the invention, main
excitation light may be a blue light component, the first color light
component may be a red light component, the second color light component
may be a green light component, and the third color light component may
be a blue light component.

[0023]With this configuration, light including a red light component, a
green light component, and a blue light component can be emitted toward
the light modulation device by using the first solid-state light source
and the second solid-state light source emitting blue light components
together.

[0024]There is a problem in that a solid-state light source which is used
in a solid-state light source device emitting a green light component has
relatively low light-emission efficiency compared to a solid-state light
source which is used in a solid-state light source device emitting a red
light component and a solid-state light source which is used in a
solid-state light source device emitting a blue light component. In
contrast, the projector according to the aspect of the invention is
configured such that a green light component is generated by using the
first solid-state light source (emitting a blue light component) which
has high light-emission efficiency compared to a solid-state light source
which is used in a solid-state light source device emitting a green light
component. Therefore, the light-emission efficiency can be increased
compared to a case where a solid-state light source device emitting a
green light component is used.

[0025]In the projector according to the aspect of the invention, the first
solid-state light source and the second solid-state light source may have
the same temperature characteristic.

[0026]With this configuration, with regard to all of the color light
components, change in the light amount with change in temperature can be
made the same. Therefore, the color balance of the projection image can
be further stabilized.

[0027]In the projector according to the aspect of the invention, main
excitation light may be ultraviolet light, the first color light
component may be a red light component, the second color light component
may be a green light component, and the third color light component may
be a blue light component.

[0028]With this configuration, light including a red light component, a
green light component, and a blue light component can be emitted toward
the light modulation device by using the first solid-state light source
emitting ultraviolet light and the second solid-state light source
emitting a blue light component.

[0029]A green light component is generated by using the first solid-state
light source (emitting ultraviolet light) which has high light-emission
efficiency compared to a solid-state light source which is used in a
solid-state light source device emitting a green light component.
Therefore, the light-emission efficiency can be increased compared to a
case where a solid-state light source device emitting a green light
component is used.

[0030]The projector according to the aspect of the invention may further
include a third solid-state light source device which includes a third
solid-state light source emitting auxiliary excitation light. The
fluorescent layer may be configured such that auxiliary excitation light
is input in a direction different from a direction in which main
excitation light is input, and the fluorescent layer may be configured to
convert auxiliary excitation light with main excitation light to light
including the first color light component and the second color light
component and to emit converted light.

[0031]With this configuration, light including the first color light
component and the second color light component can be emitted from the
first solid-state light source device by using two kinds of excitation
light of main excitation light and auxiliary excitation light. Therefore,
the projection image can be further brightened.

[0032]The projector according to the aspect of the invention may further
include a first collimation optical system parallelizing light emitted
from the first solid-state light source device, a second collimation
optical system parallelizing the third color light component emitted from
the second solid-state light source device, and a third collimation
optical system parallelizing auxiliary excitation light emitted from the
third solid-state light source device. The color light combining optical
system may be disposed in a region including an intersection between an
optical axis of the first collimation optical system, an optical axis of
the second collimation optical system, and an optical axis of the third
collimation optical system to directly transmit light, which is converted
by the fluorescent layer and emitted from the fluorescent layer, to
reflect the third color light component from the second solid-state light
source device, thereby combining light emitted from the first solid-state
light source and the third color light component with each other, and to
reflect auxiliary excitation light from the third solid-state light
source device such that auxiliary excitation light is input to the
fluorescent layer in an opposite direction to a direction in which main
excitation light is input from the first solid-state light source.

[0033]With this configuration, light (including the first color light
component and the second color light component) emitted from the first
solid-state light source device and the third color light component
emitted from the second solid-state light source device can be combined
together as parallel light.

[0034]In the projector according to the aspect of the invention, auxiliary
excitation light which is converted to parallel light by the third
collimation optical system is reflected as parallel light by the color
light combining optical system, is focused by the first collimation
optical system, and is efficiently input to the light-emission region of
the fluorescent layer. Therefore, it is possible to suppress the spread
of the light-emission region due to the third solid-state light source
device being further provided.

[0035]In the projector according to the aspect of the invention, main
excitation light may be a blue light component, the first color light
component may be a red light component, the second color light component
may be a green light component, the third color light component may be a
blue light component, and auxiliary excitation light may be a blue light
component.

[0036]With this configuration, light including a red light component, a
green light component, and a blue light component can be emitted toward
the light modulation device by using the first solid-state light source,
the second solid-state light source, and the third solid-state light
source emitting blue light components together.

[0037]A green light component is generated by using the first solid-state
light source and the third solid-state light source (emitting blue light
components together) which have high light-emission efficiency compared
to a solid-state light source which is used in a solid-state light source
device emitting a green light component. Therefore, light-emission
efficiency can be increased compared to a case where a solid-state light
source device emitting a green light component is used.

[0038]In the projector according to the aspect of the invention, the first
solid-state light source, the second solid-state light source, and the
third solid-state light source may have the same temperature
characteristic.

[0039]With this configuration, with regard to all of the color light
components, change in the light amount with change in temperature can be
made the same. Therefore, the color balance of the projection image can
be further stabilized.

[0040]In the projector according to the aspect of the invention, main
excitation light may be a blue light component, the first color light
component may be a red light component, the second color light component
may be a green light component, the third color light component may be a
blue light component, and auxiliary excitation light may be ultraviolet
light.

[0041]With this configuration, light including a red light component, a
green light component, and a blue light component can be emitted toward
the light modulation device by using the first solid-state light source
and the second solid-state light source emitting blue light components
together and the third solid-state light source emitting ultraviolet
light.

[0042]A green light component is generated by using the first solid-state
light source (emitting a blue light component) and the third solid-state
light source (emitting ultraviolet light) which have high light-emission
efficiency compared to a solid-state light source which is used in a
solid-state light source device emitting a green light component.
Therefore, light-emission efficiency can be increased compared to a case
where a solid-state light source device emitting a green light component
is used.

[0043]The projector according to the aspect of the invention may further
include an excitation light reflecting mirror disposed in front of the
color light combining optical system to directly transmit light, which is
converted by the fluorescent layer and emitted from the fluorescent
layer, and to reflect main excitation light, which is emitted while being
not converted by the fluorescent layer, toward the fluorescent layer.

[0044]With this configuration, main excitation light (blue light
component) which directly transmits the fluorescent layer while being not
converted is input again to the fluorescent layer and reused, such that
light use efficiency can be improved, and consequently the projection
image can be further brightened.

[0045]In the projector according to the aspect of the invention, main
excitation light may be ultraviolet light, the first color light
component may be a red light component, the second color light component
may be a green light component, the third color light component may be a
blue light component, and the auxiliary excitation light may be a blue
light component.

[0046]With this configuration, light including a red light component, a
green light component, and a blue light component can be emitted toward
the light modulation device by using the first solid-state light source
emitting ultraviolet light and the second solid-state light source and
the third solid-state light source emitting blue light components
together.

[0047]A green light component is generated by the first solid-state light
source (emitting ultraviolet light) and the third solid-state light
source (emitting a blue light component) which have high light-emission
efficiency compared to a solid-state light source which is used in a
solid-state light source device emitting a green light component.
Therefore, light-emission efficiency can be increased compared to a case
where a solid-state light source device emitting a green light component
is used.

[0048]The projector according to the aspect of the invention may further
include an excitation light reflecting mirror disposed in front of the
color light combining optical system to directly transmit light, which is
converted by the fluorescent layer and emitted from the fluorescent
layer, and to reflect main excitation light, which is emitted while being
not converted by the fluorescent layer, toward the fluorescent layer.

[0049]With this configuration, main excitation light (ultraviolet light)
which directly transmits the fluorescent layer while being not converted
is input again to the fluorescent layer and reused, such that light use
efficiency can be improved, and consequently the projection image can be
further brightened.

[0050]In the projector according to the aspect of the invention, main
excitation light may be ultraviolet light, the first color light
component may be a red light component, the second color light component
may be a green light component, the third color light component may be a
blue light component, and auxiliary excitation light may be ultraviolet
light.

[0051]With this configuration, light including a red light component, a
green light component, and a blue light component can be emitted toward
the light modulation device by using the first solid-state light source
and the third solid-state light source emitting ultraviolet light
together and the second solid-state light source emitting a blue light
component.

[0052]A green light component is generated by using the first solid-state
light source and the third solid-state light source (emitting ultraviolet
light together) which have high light-emission efficiency compared to a
solid-state light source which is used in a solid-state light source
device emitting a green light component. Therefore, light-emission
efficiency can be increased compared to a case where a solid-state light
source device emitting a green light component is used.

[0053]In the projector according to the aspect of the invention, the
fluorescent layer may be formed of a layer containing a YAG-based
fluorescent material, a silicate-based fluorescent material, or a
TAG-based fluorescent material.

[0054]The above-described fluorescent material can efficiently convert
excitation light (main excitation light and auxiliary excitation light)
to light including a red light component and a green light component, and
can emit converted light. Further, the fluorescent material itself has
high reliability. Therefore, with the above-described configuration, the
projection image can be further brightened, and thus a high-reliable
projector can be provided.

[0055]The YAG-based fluorescent material refers to a fluorescent material,
such as (Y,Gd)3(Al,Ga)5O12:Ce, which has a garnet crystal
structure and is based on composite oxide of yttrium and aluminum.

[0056]The silicate-based fluorescent material refers to a fluorescent
material, such as (Ca,Sr,Ba)SiO4:Eu, which is based on silicate salt
(silicate) with various components introduced.

[0057]The TAG-based fluorescent material refers to a fluorescent material,
such as Tb3Al5O12:Ce, which has a garnet crystal structure
and is based on composite oxide of terbium and aluminum.

[0058]In the projector according to the aspect of the invention, a
function may be provided to remove a yellow light component from light
from the first solid-state light source device.

[0059]With this configuration, the yellow light component can be removed
from light from the first solid-state light source device. As a result,
color reproducibility can be prevented from being deteriorated due to the
yellow light component.

[0060]In the projector according to the aspect of the invention, a
function may be provided to remove a yellow light component from light
from the first solid-state light source device. In this case, the yellow
light component which is included in light from the first solid-state
light source device can be positively used, and a brighter projection
image can be projected.

BRIEF DESCRIPTION OF THE DRAWINGS

[0061]The invention will be described with reference to the accompanying
drawings, wherein like numbers reference like elements.

[0062]FIG. 1 is a plan view showing optical systems of a projector 1000
according to a first embodiment.

[0063]FIGS. 2A and 2B are diagrams illustrating a first solid-state light
source device 20 and a second solid-state light source device 120 in the
projector 1000 of the first embodiment.

[0064]FIGS. 3A to 3C are graphs showing relative light-emission intensity
of a first solid-state light source 24, a fluorescent layer 26, and a
second solid-state light source 124 in the projector 1000 according to
the first embodiment.

[0065]FIG. 4 is a plan view showing optical systems of a projector 1002
according to a second embodiment.

[0066]FIG. 5 is a plan view showing optical systems of a projector 1004
according to a third embodiment.

[0067]FIG. 6 is a plan view showing optical systems of a projector 1006
according to a fourth embodiment.

[0068]FIG. 7 is a sectional view of a third solid-state light source
device 80 in the projector 1006 according to the fourth embodiment.

[0069]FIG. 8 is a graph showing relative light-emission intensity of a
third solid-state light source 84 in the projector 1006 according to the
fourth embodiment.

[0070]FIG. 9 is a plan view showing optical systems of a projector 1008
according to a modification.

DESCRIPTION OF EXEMPLARY EMBODIMENTS

[0071]Hereinafter, a projector according to the invention will be
described based on embodiments shown in the drawings.

First Embodiment

[0072]First, the configuration of a projector 1000 according to a first
embodiment will be described.

[0073]FIG. 1 is a plan view showing optical systems of a projector 1000
according to a first embodiment.

[0074]FIGS. 2A and 2B are diagrams illustrating a first solid-state light
source device 20 and a second solid-state light source device 120 in the
projector 1000 according to the first embodiment. FIG. 2A is a sectional
view of the first solid-state light source device 20. FIG. 2B is a
sectional view of the second solid-state light source device 120.

[0075]FIGS. 3A to 3C are graphs showing relative light-emission intensity
of a first solid-state light source 24, a fluorescent layer 26, and a
second solid-state light source 124 in the projector 1000 according to
the first embodiment. FIG. 3A is a graph showing relative light-emission
intensity of a first solid-state light source 24. FIG. 3B is a graph
showing relative light-emission intensity of a fluorescent layer 26. FIG.
3C is a graph showing relative light-emission intensity of a second
solid-state light source 124. The term "relative light-emission
intensity" refers to the characteristic regarding what level of intensity
of light with what kind of wavelength at the time of emission when a
voltage is applied in the case of a solid-state light source and when
excitation light is input in the case of a fluorescent layer. In the
graphs, the vertical axis represents relative light-emission intensity.
Light-emission intensity with a wavelength having the maximum
light-emission intensity is set to 1. In the graphs, the horizontal axis
represents a wavelength.

[0076]As shown in FIG. 1, the projector 1000 of the first embodiment
includes a first illumination device 10, a second illumination device
110, a color separating and guiding optical system 300, three liquid
crystal light modulation devices 400R, 400G, and 400B serving as a light
modulation device, a cross dichroic prism 500, and a projection optical
system 600.

[0077]The first illumination device 10 includes a first solid-state light
source device 20, a first collimation optical system 30, a dichroic
mirror 40, and a rod integrator optical system 50.

[0078]As shown in FIG. 2A, the first solid-state light source device 20 is
a light-emitting diode which has a base 22, a first solid-state light
source 24, a fluorescent layer 26, and a seal member 28, and emits light
including a red light component, a yellow light component, and a green
light component (see FIG. 3B which will be described below). The first
solid-state light source device 20 also has lead wires and the like in
addition to the above-described constituent elements, but the lead wires
and the like will not be shown or described.

[0079]The base 22 is a base on which the first solid-state light source 24
is mounted.

[0080]The first solid-state light source 24 emits a blue light component
(the peak of light-emission intensity: about 460 nm, see FIG. 3A) as main
excitation light. In FIG. 3A, reference numeral B denotes a color light
component which is emitted as main excitation light (blue light
component) from the first solid-state light source 24. The first
solid-state light source 24 includes gallium nitride as a main component
and has a pn junction-type structure. The first solid-state light source
may not have a pn junction-type structure, but may have a double
heterojunction-type structure, a quantum well junction-type structure, or
the like.

[0081]A reflecting layer (not shown) is formed between the first
solid-state light source 24 and the base 22. A blue light component
emitted from the first solid-state light source toward the base 22 is
reflected toward the fluorescent layer 26 by the reflecting layer.

[0082]The fluorescent layer 26 is formed of a layer containing a
(Y,Gd)3(Al,Ga)5O12:Ce which is a YAG-based fluorescent
material, and is disposed in the illuminated region of the first
solid-state light source 24. The fluorescent layer 26 is most efficiently
excited by a blue light component with a wavelength of about 460 nm. As
shown in FIG. 3B, the fluorescent layer 26 converts a blue light
component emitted from the first solid-state light source 24 to light
including a red light component (the peak of light-emission intensity:
about 610 nm), a yellow light component (the peak of light-emission
intensity: about 580 nm), and a green light component (the peak of
light-emission intensity: about 550 nm), and emits converted light.
Referring to FIG. 3B, reference numeral R denotes a color light
component, which can be used as a red light component, from among the
light components emitted from the fluorescent layer 26. Reference numeral
G denotes a color light component, which can be used as a green light
component, from among the light components emitted from the fluorescent
layer 26. Reference numeral Y denotes a color light component which is
emitted as a yellow light component from the fluorescent layer.

[0083]The seal member 28 is formed of transparent epoxy resin, and
protects the first solid-state light source 24 and the fluorescent layer
26.

[0084]As shown in FIG. 1, the first collimation optical system 30 includes
a convex meniscus lens 32 which suppresses the spread of light from the
first solid-state light source device 20, and a convex lens 34 which
parallelizes light from the convex meniscus lens 32. As a whole, the
first collimation optical system 30 has a function to parallelize light
from the first solid-state light source device 20.

[0085]The dichroic mirror 40 is a color light combining optical system
which combines light emitted from the first solid-state light source
device 20 and a blue light component emitted from the second solid-state
light source device 120 (which will be described below). The dichroic
mirror 40 is disposed in a region including an intersection between an
optical axis of the first collimation optical system 30 and an optical
axis of a second collimation optical system 130 (which will be described
below) to directly transmit light, which is converted by the fluorescent
layer 26 and emitted from the fluorescent layer 26, and to reflect the
blue light component from the second solid-state light source device 120.
Specifically, the dichroic mirror 40 is a mirror which has a wavelength
selective transmission film formed on a substrate to reflect a blue light
component and to transmit a red light component, a yellow light
component, and a green light component.

[0086]The rod integrator optical system 50 includes a convex lens 52, a
rod lens 54, and a convex lens 56.

[0087]The convex lens 52 focuses parallel light from the first collimation
optical system 30 and parallel light (blue light component which will be
described below) from the second collimation optical system 130 reflected
by the dichroic mirror 40, and guides focused light to the incidence
surface of the rod lens 54.

[0088]The rod lens 54 is a solid columnar lens. The rod lens 54 multiply
reflects light input from the incidence surface within the plane to make
light uniform, and emits light having a uniform in-plane light-emission
intensity distribution from the emission surface. As the rod lens, a
hollow columnar lens, instead of a solid columnar lens, may be used.

[0090]The second illumination device 110 includes a second solid-state
light source device 120 and a second collimation optical system 130.

[0091]As shown in FIG. 2B, the second solid-state light source device 120
is a light-emitting diode which has a base 122, a second solid-state
light source 124, and a seal member 128, and emits a blue light component
(see FIG. 3c which will be described below). The second solid-state light
source device 120 has lead wires and the like in addition to the
above-described constituent elements, but the lead wires and the like
will not be shown or described.

[0092]As shown in FIG. 3c, the second solid-state light source 124 emits a
blue light component (the peak of light-emission intensity: about 460 nm)
as a color light component. In FIG. 3c, reference numeral B denotes a
color light component which is emitted as a color light component (blue
light component) from the second solid-state light source 124.

[0093]The base 122, the second solid-state light source 124, and the seal
member 128 respectively have the same configuration as the base 22, the
first solid-state light source 24, and the seal member 28, thus detailed
description thereof will not be repeated.

[0094]The first solid-state light source 24 and the second solid-state
light source 124 are formed of the same material by the same
manufacturing method and have the same structure. For this reason, the
first solid-state light source 24 and the second solid-state light source
124 have the same temperature characteristic, such that change in the
light amount with change in temperature is identical.

[0095]As shown in FIG. 1, the second collimation optical system 130
includes a convex meniscus lens 132 suppressing the spread of the blue
light component from the second solid-state light source device 120, and
a convex lens 134 parallelizing the blue light component from the convex
meniscus lens 132. As a whole, the second collimation optical system 130
has a function to parallelize the blue light component from the second
solid-state light source device 120.

[0096]The color separating and guiding optical system 300 includes a
dichroic mirror 310 which is disposed upstream of the optical path,
dichroic mirrors 320 and 330 which are disposed downstream of the optical
path, reflecting mirrors 340 and 350, and relay lenses 360 and 370. The
color separating and guiding optical system 300 has a function to
separate light from the convex lens 56 into three color light components
of a red light component, a green light component, and a blue light
component, and to guide the respective color light components to the
liquid crystal light modulation devices 400R, 400G, and 400B to be
illuminated.

[0097]The dichroic mirrors 310, 320, and 330 are optical elements which
have a wavelength selective transmission film formed on the substrate to
reflect light having a predetermined wavelength region and to transmit
light having another wavelength region.

[0098]The dichroic mirror 310 is a dichroic mirror which reflects a red
light component and a yellow light component, and transmits a green light
component and a blue light component.

[0099]The dichroic mirror 320 is a dichroic mirror which reflects a green
light component, and transmits a blue light component.

[0100]The dichroic mirror 330 is a dichroic mirror which reflects a red
light component, and transmits a yellow light component. The yellow light
component having transmitted the dichroic mirror 330 is removed outside
the system. That is, the projector 1000 has a function to remove the
yellow light component by the dichroic mirror 330. In FIG. 1, a
solid-line arrow (see reference numeral Y) extending from the dichroic
mirror 330 denotes the yellow light component having transmitted the
dichroic mirror 330.

[0101]The red light component having been reflected by the dichroic mirror
310 is reflected by the dichroic mirror 330 and input to the image
forming region of the liquid crystal light modulation device 400R for a
red light component.

[0102]The green light component from among the green light component and
the blue light component having transmitted the dichroic mirror 310 is
reflected by the dichroic mirror 320 and input to the image forming
region of the liquid crystal light modulation device 400G for a green
light component. Meanwhile, the blue light component transmits the
dichroic mirror 320, then transmits the relay lens 360, the
incidence-side reflecting mirror 340, the relay lens 370, and the
emission-side reflecting mirror 350, and is subsequently input to the
image forming region of the liquid crystal light modulation device 400B
for a blue light component. The relay lenses 360 and 370 and the
reflecting mirrors 340 and 350 have a function to guide the blue light
component having transmitted the dichroic mirror 320 to the liquid
crystal light modulation device 400B.

[0103]The reason why the relay lenses 360 and 370 and the reflecting
mirrors 340 and 350 are provided in the optical path of the blue light
component is to prevent degradation in light use efficiency due to light
divergence or the like since the length of the optical path of the blue
light component is longer than the length of the optical path of other
color light components. Although in the projector 1000 of the first
embodiment, since the length of the optical path of the blue light
component is long, such configuration is made, the length of the optical
path of the red light component may be extended, and the relay lenses 360
and 370 and the reflecting mirrors 340 and 350 may be used in the optical
path of the red light component.

[0104]The liquid crystal light modulation devices 400R, 400G, and 400B
modulate the input color light components in accordance with image
information to form a color image, and are illuminated by the first
illumination device 10 and the second illumination device 110. Though not
shown, incidence-side polarizing plates are respectively disposed between
the dichroic mirror 330 and the liquid crystal light modulation device
400R, between the dichroic mirror 320 and the liquid crystal light
modulation device 400G, and between the reflecting mirror 350 and the
liquid crystal light modulation device 400B. Emission-side polarizing
plates are respectively disposed between the liquid crystal light
modulation devices 400R, 400G, and 400B and the cross dichroic prism 500.
Light modulation of the respective input color light components is
carried out by the incidence-side polarizing plates, the liquid crystal
light modulation devices 400R, 400G, and 400B, and the emission-side
polarizing plates.

[0105]The liquid crystal light modulation devices 400R, 400G, and 400B are
formed by sealing liquid crystal serving as an electro-optical material
between a pair of transparent glass substrates. For example, each of the
liquid crystal light modulation devices 400R, 400G, and 400B modulates
the polarization direction of one linearly polarized light emitted from
the corresponding incidence-side polarizing plate in accordance with a
given image signal with a polysilicon TFT as a switching element.

[0106]The cross dichroic prism 500 is an optical element which combines
modulated optical images for the respective color light components
emitted from the emission-side polarizing plates to form a color image.
The cross dichroic prism 500 is formed by bonding four rectangular prisms
to each other and substantially has a square shape in plan view. A
dielectric multilayer film is formed at an interface having a
substantially X shape of the bonded rectangular prisms. A dielectric
multilayer film formed at one interface having a substantially X shape
reflects the red light component, and a dielectric multilayer film formed
at another interface reflects the blue light component. These dielectric
multilayer films cause the red light component and the blue light
component to be bent and arranged in the traveling direction of the green
light component, such that the three color light components are combined.

[0107]The color image emitted from the cross dichroic prism 500 is
enlarged and projected by the projection optical system 600 to form an
image on a screen SCR.

[0108]Next, the effects of the projector 1000 according to the first
embodiment will be described.

[0109]According to the projector 1000 of the first embodiment, the two
color light components (red light component and green light component)
emitted from the first solid-state light source device 20 and one color
light component (blue light component) emitted from the second
solid-state light source device 120 are used as the three color light
components (red light component, green light component, and blue light
component) which are modulated by the liquid crystal light modulation
devices 400R, 400G, and 400B. Therefore, the thermal load imposed on the
respective solid-state light source devices can be reduced compared to a
projector which includes a single solid-state light source device. As a
result, the projection image can be brightened compared to a projector
which includes a single solid-state light source device.

[0110]According to the projector 1000 of the first embodiment, the two
color light components (red light component and green light component)
from among the three color light components (red light component, green
light component, and blue light component) which are modulated by the
liquid crystal light modulation devices 400R, 400G, and 400B are
generated by the common solid-state light source (first solid-state light
source 24). Therefore, the color balance of the projection image can be
stabilized compared to a projector which includes separate three
solid-state light source devices for the respective color light
components.

[0111]As a result, the projector 1000 of the first embodiment can brighten
the projection image compared to a projector which includes a single
solid-state light source device, and can stabilize the color balance of
the projection image compared to a projector which includes separate
three solid-state light source devices for respective color light
components.

[0112]The projector 1000 of the first embodiment includes the dichroic
mirror 40 which combines light emitted from the first solid-state light
source device 20 and the blue light component emitted from the second
solid-state light source device 120 with each other. Therefore, it is not
necessary to provide exclusive-use optical systems for light emitted from
the first solid-state light source device 20 and the blue light component
emitted from the second solid-state light source device 120, such that
the number of components can be reduced.

[0113]According to the projector 1000 of the first embodiment, a full
color projector can be constituted by using the color separating and
guiding optical system 300 which is widely used at present.

[0114]The projector 1000 of the first embodiment includes the first
collimation optical system 30 and the second collimation optical system
130. The dichroic mirror 40 is disposed in the region including the
intersection between the optical axis of the first collimation optical
system 30 and the optical axis of the second collimation optical system
130. Therefore, light (including red light component and green light
component) emitted from the first solid-state light source device 20 and
the blue light component emitted from the second solid-state light source
device 120 can be combined together as parallel light.

[0115]According to the projector 1000 of the first embodiment, main
excitation light is a blue light component, the first color light
component is a red light component, the second color light component is a
green light component, and the third color light component is a blue
light component. Therefore, light including a red light component, a
green light component, and a blue light component can be emitted toward
the liquid crystal light modulation devices 400R, 400G, and 400B by using
the first solid-state light source 24 and the second solid-state light
source 124 emitting blue light components together.

[0116]According to the projector 1000 of the first embodiment, the green
light component is generated by using the first solid-state light source
24 (emitting the blue light component) which has high light-emission
efficiency compared to the solid-state light source which is used in the
solid-state light source device emitting the green light component.
Therefore, light-emission efficiency can be increased compared to a case
where the solid-state light source device emitting the green light
component is used.

[0117]According to the projector 1000 of the first embodiment, the first
solid-state light source 24 and the second solid-state light source 124
have the same temperature characteristic. Therefore, with regard to all
of the color light components, changes in the light amount with change in
temperature are made the same, such that the color balance of the
projection image can be further stabilized.

[0118]According to the projector 1000 of the first embodiment, the
fluorescent layer 26 is formed of a layer containing a YAG-based
fluorescent material, (Y,Gd)3(Al,Ga)5O12:Ce. Therefore,
the projection image can be further brightened, and a high-reliable
projector can be obtained.

[0119]According to the projector 1000 of the first embodiment, the
dichroic mirror 330 has a function to remove the yellow light component
from light from the first solid-state light source device 20. Therefore,
the yellow light component can be removed from light from the first
solid-state light source device 20. As a result, color reproducibility
can be prevented from being deteriorated due to the yellow light
component.

Second Embodiment

[0120]FIG. 4 is a plan view showing optical systems of a projector 1002
according to a second embodiment.

[0121]The projector 1002 of the second embodiment basically has the same
configuration as the projector 1000 of the first embodiment, but a first
illumination device has the configuration different from that in the
projector 1000 of the first embodiment.

[0122]That is, in the projector 1002 of the second embodiment, as shown in
FIG. 4, a first illumination device 12 further includes an excitation
light reflecting mirror 60 which is located at the back of the
collimation optical system 30 to directly transmit light (red light
component, yellow light component, and green light component), which is
converted by the fluorescent layer and emitted from the fluorescent layer
26, and to reflect excitation light (blue light component), which is
emitted while being not converted by the fluorescent layer 26, toward the
fluorescent layer 26.

[0123]As described above, in the projector 1002 of the second embodiment,
the first illumination device has the configuration different from that
in the projector 1000 of the first embodiment; however, the two color
light components (red light component and green light component) emitted
from the first solid-state light source device 20 and one color light
component (blue light component) emitted from the second solid-state
light source device 120 are used as the three color light components (red
light component, green light component, and blue light component) which
are modulated by the liquid crystal light modulation devices 400R, 400G,
and 400B, and the two color light components (red light component and
green light component) from among the three color light components (red
light component, green light component, and blue light component) which
are modulated by the liquid crystal light modulation devices 400R, 400G,
and 400B are generated by using the common solid-state light source
(first solid-state light source 24). Therefore, similarly to the
projector 1000 of the first embodiment, the projection image can be
brightened compared to a projector which includes a single solid-state
light source device, and the color balance of the projection image can be
stabilized compared to a projector which includes separate solid-state
light source devices for respective color light components.

[0124]The projector 1002 of the second embodiment further includes the
excitation light reflecting mirror 60. For this reason, main excitation
light (blue light component) having directly transmitted the fluorescent
layer 26 is input again to the fluorescent layer 26 and reused, such that
light use efficiency can be improved, and consequently the projection
image can be further brightened. Further, the main excitation light (blue
light component) can be removed from light from the first solid-state
light source device 20. As a result, color reproducibility or light
modulation device can be prevented from being deteriorated due to main
excitation light (blue light component).

[0125]In the projector 1002 of the second embodiment, main excitation
light (blue light component) directly transmits the fluorescent layer 26
and is converted to parallel light by the first collimation optical
system 30. Then, parallel light is reflected by the excitation light
reflecting mirror 60, is focused by the first collimation optical system
30, and is efficiently input to the light-emission region of the
fluorescent layer 26. Therefore, it is possible to suppress the spread of
the light-emission region due to the excitation light reflecting mirror
60 being further provided.

[0126]The projector 1002 of the second embodiment has the same
configuration as the projector 1000 of the first embodiment, excluding
the configuration of the first illumination device. Therefore, the
projector 1002 of the second embodiment also has the relevant effects
from among the effects of the projector 1000 of the first embodiment.

Third Embodiment

[0127]FIG. 5 is a plan view showing optical systems of a projector 1004
according to a third embodiment.

[0128]The projector 1004 of the third embodiment basically has the same
configuration as the projector 1000 of the first embodiment, but a first
illumination device has the configuration different from that in the
projector 1000 of the first embodiment.

[0129]That is, in the projector 1004 of the third embodiment, as shown in
FIG. 5, a first illumination device 14 includes a lens integrator optical
system 70, instead of the rod integrator optical system 50. The lens
integrator optical system 70 includes a first lens array 72, a second
lens array 74, and a superimposing lens 76.

[0130]As described above, in the projector 1004 of the third embodiment,
the first illumination device has the configuration different from that
in the projector 1000 of the first embodiment; however, the two color
light components (red light component and green light component) emitted
from the first solid-state light source device 20 and one color light
component (blue light component) emitted from the second solid-state
light source device 120 are used as the three color light components (red
light component, green light component, and blue light component) which
are modulated by the liquid crystal light modulation devices 400R, 400G,
and 400B, and the two color light components (red light component and
green light component) from among the three color light components (red
light component, green light component, and blue light component) which
are modulated by the liquid crystal light modulation devices 400R, 400G,
and 400B are generated by the common solid-state light source (first
solid-state light source 24). Therefore, similarly to the projector 1000
of the first embodiment, the projection image can be brightened compared
to a projector which includes a single solid-state light source device,
and the color balance of the projection image can be stabilized compared
to a projector which includes separate solid-state light source devices
for respective color light components.

[0131]The projector 1004 of the third embodiment has the same
configuration as the projector 1000 of the first embodiment, excluding
the configuration of the first illumination device. Therefore, the
projector 1004 of the third embodiment also has the relevant effects from
among the effects of the projector 1000 of the first embodiment.

Fourth Embodiment

[0132]FIG. 6 is a plan view showing optical systems of a projector 1006
according to a fourth embodiment.

[0133]FIG. 7 is a sectional view of a third solid-state light source
device 80 in the projector 1006 according to the fourth embodiment.

[0134]FIG. 8 is a graph showing relative light-emission intensity of a
third solid-state light source 84 in the projector 1006 according to the
fourth embodiment.

[0135]The projector 1006 of the fourth embodiment basically has the same
configuration as the projector 1000 of the first embodiment, but a first
illumination device has the configuration different from that in the
projector 1000 of the first embodiment.

[0136]That is, in the projector 1006 of the fourth embodiment, as shown in
FIGS. 6 and 7, a first illumination device 16 further includes a third
solid-state light source device 80 which includes a third solid-state
light source 84 emitting auxiliary excitation light (blue light
component), and a third collimation optical system 90. Thus, the
fluorescent layer 26 is configured to convert auxiliary excitation light
(blue light component) to light including a red light component and a
green light component, and to emit converted light. The dichroic mirror
40 which is a color light combining optical system is disposed in a
region including an intersection between an optical axis of the first
collimation optical system 30, an optical axis of the second collimation
optical system 120, an optical axis of the third collimation optical
system 90. The dichroic mirror 40 further has a function to reflect
auxiliary excitation light (blue light component) from the third
solid-state light source device 80, and to input auxiliary excitation
light (blue light component) to the fluorescent layer 26 in an opposite
direction to a direction in which main excitation light (blue light
component) from the first solid-state light source 24 is input.

[0137]As shown in FIG. 7, the third solid-state light source device 80 is
a light-emitting diode which has a base 82, a third solid-state light
source 84, and a seal member 88, and emits a blue light component (see
FIG. 8 which will be described below). The third solid-state light source
device 80 has lead wires and the like in addition to the above-described
constituent elements, but the lead wires and the like will not be shown
or described.

[0139]The base 82, the third solid-state light source 84, and the seal
member 88 respectively have the same configuration as the base 22, the
first solid-state light source 24, and the seal member 28, thus detailed
description thereof will not be shown or described.

[0140]The first solid-state light source 24, the second solid-state light
source 124, and the third solid-state light source 84 are formed of the
same material by the same manufacturing method and have the same
structure. For this reason, the first solid-state light source 24, the
second solid-state light source 124, the third solid-state light source
84 have the same temperature characteristic, such that change in the
light amount with change in temperature is identical.

[0141]As shown in FIG. 6, the third collimation optical system 90 includes
a convex meniscus lens 92 suppressing the spread of the blue light
component from the third solid-state light source device 80, and a convex
lens 94 parallelizing the blue light component from the convex meniscus
lens 92. As a whole, the third collimation optical system 90 has a
function to parallelize the blue light component from the third
solid-state light source device 80.

[0142]As described above, in the projector 1006 of the fourth embodiment,
the first illumination device has the configuration different from that
in the projector 1000 of the first embodiment; however, the two color
light components (red light component and green light component) emitted
from the first solid-state light source device 20 and one color light
component (blue light component) emitted from the second solid-state
light source device 120 are used as the three color light components (red
light component, green light component, and blue light component) which
are modulated by the liquid crystal light modulation devices 400R, 400G,
and 400B, and the two color light components (red light component and
green light component) from among the three color light components (red
light component, green light component, and blue light component) which
are modulated by the liquid crystal light modulation devices 400R, 400G,
and 400B are generated by using the common solid-state light source
(first solid-state light source 24 and third solid-state light source
84). Therefore, similarly to the projector 1000 of the first embodiment,
the projection image can be brightened compared to a projector which
includes a single solid-state light source device, and the color balance
of the projection image can be stabilized compared to a projector which
includes separate solid-state light source devices for respective color
light components.

[0143]The projector 1006 of the fourth embodiment further includes the
third solid-state light source device 80 which includes the third
solid-state light source 84 emitting auxiliary excitation light (blue
light component). Therefore, light including a red light component and a
green light component can be emitted from the first solid-state light
source device 20 by using two kinds of excitation light of main
excitation light and auxiliary excitation light (which are both blue
light components), and the projection image can be further brightened.

[0144]The projector 1006 of the fourth embodiment further includes the
third collimation optical system 90. Thus, auxiliary excitation light
(blue light component) which is converted to parallel light by the third
collimation optical system 90 is reflected as parallel light by the
dichroic mirror 40, is focused by the first collimation optical system
30, and is efficiently input to the light-emission region of the
fluorescent layer 26. Therefore, it is possible to suppress the spread of
the light-emission region due to the third solid-state light source
device 80 being further provided.

[0145]According to the projector 1006 of the fourth embodiment, main
excitation light is a blue light component, the first color light
component is a red light component, the second color light component is a
green light component, the third color light component is a blue light
component, and auxiliary excitation light is a blue light component.
Therefore, light including a red light component, a green light
component, and a blue light component can be emitted toward the light
modulation device by using the first solid-state light source 24, the
second solid-state light source 124, and the third solid-state light
source 84 emitting blue light components together.

[0146]According to the projector 1006 of the fourth embodiment, a green
light component is generated by using the first solid-state light source
24 and the third solid-state light source 84 (emitting blue light
components together) which have high light-emission efficiency compared
to a solid-state light source which is used in a solid-state light source
device emitting a green light component. Therefore, light-emission
efficiency can be increased compared to a case where a solid-state light
source device emitting a green light component is used.

[0147]According to the projector 1006 of the fourth embodiment, the first
solid-state light source 24, the second solid-state light source 124, and
the third solid-state light source device 84 have the same temperature
characteristic. Therefore, with regard to all of the color light
components, changes in the light amount with change in temperature are
made the same, such that the color balance of the projection image can be
further stabilized.

[0148]Although the invention has been described on the basis of the
foregoing embodiments, the invention is not limited to the foregoing
embodiments. The invention may be carried out in various forms without
departing from the scope and spirit of the invention. For example, the
following modifications may be made.

[0149](1) Although in the foregoing embodiments, the fluorescent layer 26
is formed of a layer containing (Y,Gd)3(Al,Ga)5O12:Ce, the
invention is not limited thereto. For example, the fluorescent layer may
be formed of a layer containing a YAG-based fluorescent material other
than (Y,Gd)3(Al,Ga)5O12:Ce, a layer containing a
silicate-based fluorescent material, or a layer containing a TAG-based
fluorescent material. Further, the fluorescent layer may be formed of a
layer containing a mixture of a fluorescent material which converts
excitation light to a red light component and a fluorescent material
which converts excitation light to a green light component.

[0150](2) Although in the foregoing embodiments, a transmission-type
projector is used, the invention is not limited thereto. For example, a
reflection-type projector may be used. The term "transmission-type" used
herein means a type, such as a transmission-type liquid crystal display
or the like, in which a light modulation device serving as a light
modulation unit transmits light, and the term "reflection-type" means a
type, such as a reflection-type liquid crystal display or the like, in
which a light modulation device serving as a light modulation unit
reflects light. Even when the invention is applied to a reflection-type
projector, the same effects as in a transmission-type projector can be
obtained.

[0151](3) Although in the foregoing embodiments, a liquid crystal light
modulation device is used as a light modulation device for a projector,
the invention is not limited thereto. As a light modulation device, in
general, any device may be used insofar as the device modulates incident
light in accordance with image information. For example, a
micromirror-type light modulation device or the like may be used. As a
micromirror-type light modulation device, for example, DMD (Digital
Micromirror Device) (Trademark of TI Inc.) may be used.

[0152](4) Although in the foregoing embodiments, the respective
solid-state light source devices are light-emitting diodes, the invention
is not limited thereto.

[0154](5) Although in the first to third embodiments, main excitation
light is a blue light component, the invention is not limited thereto.
Main excitation light may be ultraviolet light. With this configuration,
light including a red light component, a green light component, and a
blue light component can be emitted from the first illumination device
toward the light modulation device, and light-emission efficiency can be
increased compared to a case where a solid-state light source device
emitting a green light component is used.

[0155](6) In the first to third embodiments, when main excitation light is
ultraviolet light, the first color light component may be a green light
component, the second color light component may be a blue light
component, and the third color light component may be a red light
component. Further, the first color light component may be a red light
component, the second color light component may be a blue light
component, and the third color light component may be a green light
component.

[0156](7) Although in the fourth embodiment, main excitation light and
auxiliary excitation light are both blue light components, the invention
is not limited thereto. Main excitation light may be a blue light
component, and auxiliary excitation light may be ultraviolet light.
Further, main excitation light may be ultraviolet light, and auxiliary
excitation light may be a blue light component. In addition, main
excitation light and auxiliary excitation light may be both ultraviolet
light. With this configuration, light including a red light component, a
green light component, and a blue light component can be emitted from the
first illumination device toward the light modulation device, and
light-emission efficiency can be increased compared to a case where a
solid-state light source device emitting a green light component is used.

[0157](8) In the fourth embodiment, when main excitation light is a blue
light component, and auxiliary excitation light is ultraviolet light, or
when main excitation light is ultraviolet light, and auxiliary excitation
light is a blue light component, an excitation light reflecting mirror
may be further provided which is disposed in front of the color light
combining optical system (dichroic mirror) to directly transmit light
emitted from the fluorescent layer and to reflect main excitation light,
which is emitted while being not converted by the fluorescent layer,
toward the fluorescent layer. With this configuration, main excitation
light which directly transmits the fluorescent layer while being not
converted is input again to the fluorescent layer and reused, such that
light use efficiency can be improved, and consequently the projection
image can be further brightened.

[0158](9) Although in the foregoing embodiments, the projector has a
function to remove a yellow light component from the first solid-state
light source device 20, the invention is not limited thereto. For
example, the projector may not have a function to remove a yellow light
component. In this case, the yellow light component included in light
emitted from the first illumination device can be positively used, such
that a brighter projection image can be projected. Further, when the
yellow light component is not removed, the yellow light component is
modulated by using a light modulation device different from that for a
red light component or a green light component, such that a projection
image having more excellent color reproducibility can be projected, in
addition to the above-described effects.

[0159](10) In the foregoing embodiments, as shown in FIG. 9, a
reflection-type polarizing plate 62 may be further provided which is
located at the back of the first collimation optical system 30 to
directly transmit one polarized component (for example, s polarized
component) from among polarized components included in light emitted from
the first solid-state light source device 20 and to reflect another
polarized component (for example, p polarized component) toward the
fluorescent layer 26. FIG. 9 is a plan view showing optical systems of a
projector 1008 according to a modification. The reflection-type
polarizing plate 62 is, for example, a wire grid polarizing plate which
has fine metal wires disposed in a lattice shape at specific pitches. In
FIG. 9, a solid-line arrow (see reference numeral R(p),G(p),Y(p))
extending from the reflection-type polarizing plate 62 denotes another
polarized component (p polarized component) reflected by the
reflection-type polarizing plate 62. With this configuration, another
polarized component (p polarized component) is returned again to the
fluorescent layer 26 and reflected by the surface of the fluorescent
layer 26, such that part of another polarized component (p polarized
component) is converted to one polarized component (s polarized
component) and reused. Therefore, light use efficiency can be improved,
and consequently the projection image can be further brightened.

[0160](11) In the foregoing embodiments, the projector may further include
a polarization conversion device. The polarization conversion device is a
polarization conversion element which converts light including one
polarized component and another polarized component to substantially one
linearly polarized light with a polarization direction arranged.

[0161](12) Although in the foregoing embodiments, each collimation optical
system includes two lenses of the convex meniscus lens and the convex
lens, the invention is not limited thereto. For example, the collimation
optical system may include only one lens or may include three or more
lenses.

[0162](13) The shape of each of the lenses which are used in the optical
path of the projector in each of the foregoing embodiments is not limited
to those described in the foregoing embodiments. If necessary, lenses
having various shapes may be used.

[0163](14) Although in the foregoing embodiments, an example where a
projector uses three liquid crystal light modulation devices has been
described, the invention is not limited to this example. The invention
may be applied to a projector which uses one, two, or four or more liquid
crystal light modulation devices.

[0164](15) The invention may be applied to a front projection-type
projector which projects a projection image from an observation side, or
a rear projection-type projector which projects a projection image from
an opposite side to the observation side.